The Royal Society Report - Push-Pull

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cannot hope to do justice to the complete issue. Instead we offer a tight focus on the possible contributions of biological science and technology, while remaining aware of the context in which this science sits and the necessity of a multidisciplinary approach. There are countless aspects of food systems, such as aquaculture, livestock, consumption and supply chains that demand attention beyond the references we provide. Similarly, there are areas of expertise and technology, including social sciences, economics, climatology, engineering, chemistry and in particular the use of agrochemicals, that are relevant but beyond the scope of this report. Debates about the role of science and technology in food production have proved contentious in the past. Our report looks at a variety of approaches, and considers their future opportunities as well as the risks, complexities and uncertainties presented through research and implementation. As well as providing a rigorous scientific assessment, we hope this report can help to start a constructive debate about the future of agriculture around the world and the contribution that might be offered by UK science. This report’s next chapter assesses the technical and environmental constraints of food crop production such as water shortages, incidence of disease and rising temperatures. Chapter 3 considers in more detail the possibilities provided by the biological sciences for addressing some of these challenges. Chapter 4 addresses the impacts—intended and unintended—of different technological approaches to agriculture, considering environmental, health and socioeconomic issues. The final chapter contains our conclusions and recommendations for policy makers. Chapter 3 contains case studies of science and technology in different contexts to illustrate the complexity of agriculture and the necessity of specific solutions for specific problems. Our case studies tell stories of where, why and how science has made a difference to food production. 1.10 Conduct of the study A working group chaired by Sir David Baulcombe FRS was established to undertake this study. The working group first met in July 2008 and had a further seven meetings. The full membership of the working group is given at the start of this report. The working group were shocked and saddened by the death of Professor Mike Gale FRS soon after the final meeting. This report has benefited hugely from his contributions and is dedicated to him. In order to obtain views from a wide range of experts, a call for evidence was issued on 7 August 2008 with a closing date of 6 October 2008. Responses were received from a range of individual academics, research institutes, industry representatives and non-governmental organisations. Details of the organisations and individuals who submitted written evidence are listed at the end of the report, and the evidence is available on the Royal Society website (royalsociety.org). An oral evidence session at the Society and an evidencegathering workshop in India were held in October 2008. A workshop with UK-based non-governmental organisations was held in May 2009. Reports of these workshops are available on the Society’s website. All this evidence informed the working group’s discussions, conclusions and recommendations. We are grateful to everyone who responded to the call for evidence, participated in the workshops and submitted additional evidence. 10 I October 2009 I Reaping the Benefits The Royal Society
2 Constraints on future food crop production Summary The constraints on food crop production and distribution differ between regions and, in particular, between industrialised and developing countries. In most areas the effects of climate change will further exacerbate the stresses on crop plants, potentially leading to catastrophic yield reductions. Fresh water availability is a major limiting factor on agricultural productivity. Improvements in the water use efficiency of plants in irrigated systems present a significant challenge, particularly in the face of climate change. Soils are another essential but non-renewable resource for food crop production. Maintenance of soil fertility, health and nutrient availability is vital. Significant losses in crop yields occur through pests, diseases and weed competition; they account for a major inefficiency of resource use (eg water, fertiliser, energy and labour). Reducing these losses represents one of the most accessible means of increasing food supplies. The need to reduce greenhouse gas emissions means that agriculture will have to become less reliant on sources of non-renewable energy derived from fossil fuels. Ensuring the diversity of crop germplasm to facilitate crop breeding in a changing climate is just one of several challenges that need to be met to ensure resilience of production. This chapter describes the many constraints that limit the production of food crops globally including soil fertility, water availability and the incidence of pests, diseases and weeds. These constraints are variable with climate change and differ greatly between industrialised and developing countries, for social, economic and geographic reasons. In industrialised countries there is typically much better access to irrigation, chemicals for disease and pest control, synthetic fertilisers and quality seeds, which substantially account for their higher yields. Chapter 3 considers the specific biological science-based technologies that could help address these various challenges. 2.1 Climate change Climate change will aggravate the effects on crops of stresses such as heat, drought, salinity and submergence in water (IPCC 2007b). This conclusion is starkly illustrated by Lobell et al. (2008), who have conducted an analysis of climate risks for crops in 12 food-insecure regions. The study identified adaptation priorities, based on statistical crop models and climate projections for 2030. Their analysis reinforces the importance of improved crop germplasm (based on the access to and use of crop genetic resources collections) and improved agronomic practices as a strategy for climate change adaptation in agriculture. The important conclusion of their study is that there are a few target crops that will be particularly vulnerable to climate change in different regions. Adaptation strategies focused on these crops must be carried out in the face of other constraints such as labour shortages and rising energy costs. More specific climate change-related constraints are considered in the following sections. 2.2 Water Of all the biotic and abiotic stresses affecting crop yield, drought has probably the greatest limiting effect (Boyer 1982). A high priority for the future is to develop genotypes that yield significantly with reduced amounts of water; this is discussed further in Section 3.3.2. This should be combined with the development of cropping systems where available water can be used with much greater efficiency. Increased variability in rainfall will lead to a greater risk of drought during cropping seasons in many regions of the world. Rising temperature will increase rates of water loss to the atmosphere from plants and soil. Predictions also suggest large increases (hundreds of millions) in the number of people who will be exposed to increased water stress (IPCC 2008) across greater areas (OECD 2006). Although total water supply may increase in some regions, precipitation will be more variable and there will be additional risks of poor water quality and flooding, as well as salt water flooding in some regions. 2.2.1 Water and yield Plants require water for growth and tissue expansion (Steduto et al. 2009). However, more than 90% of the water required by terrestrial plants is not ‘used’ in metabolism but is lost through transpiration (T). A distinction is often made between ‘water-limited’ and ‘wet’ environments. What is usually meant by the former is that water availability ‘limits’ crop productivity to below the maximum or potential production when water supply is less than the demand for water set by atmospheric conditions. Yield of most crops is restricted by water availability in most environments and ensuring appropriate water availability to plants during important developmental stages is a key challenge to increasing food crop production. There is an important difference between crops that remain alive during very severe droughts but may never yield significantly (desiccation resistance) and crops that sustain yields under water scarcity (drought resistance). The term water use efficiency (WUE) can be used on different scales: harvest, farm, field, plant and down to the leaf. It can be applied to the water lost in producing just the economic yield, or the biological yield which can be all the above-ground biomass, or (more rarely) the total biomass. It can include or exclude the evaporation from the soil and plant surfaces directly. It can also be applied across different timescales. At the crop or field scale, it can be The Royal Society Reaping the Benefits I October 2009 I 11
Page 1 and 2: Reaping the benefits Science and th
Page 3 and 4: Reaping the benefi ts: science and
Page 5 and 6: Reaping the benefi ts: science and
Page 7 and 8: Foreword Lord Rees of Ludlow OM Pre
Page 9 and 10: Membership of working group The mem
Page 11 and 12: Summary Food security is one of thi
Page 13 and 14: 1 Introduction Summary Food securit
Page 15 and 16: Figure 1.4. Changes in per capita a
Page 17 and 18: of R&D can take many years to filte
Page 19 and 20: protected area status. The ecosyste
Page 21: governments and NGOs. The report co
Page 25 and 26: y high temperatures during and afte
Page 27 and 28: salt affected (Athar & Ashraf 2009)
Page 29 and 30: Table 2.1. Major pests of maize, ri
Page 31 and 32: depends to a great extent on the av
Page 33 and 34: 3 Developments in biological scienc
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Page 39 and 40: Case study 3.3. Seed mixtures to in
Page 41 and 42: Case study 3.4. Integrated pest man
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Page 45 and 46: host defences have been identified
Page 47 and 48: eliminated), and external inputs su
Page 49 and 50: Cost Costs of developing biofortifi
Page 51 and 52: 4 Consequences and complications of
Page 53 and 54: Soil and water conservation, contou
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Page 57 and 58: e linked to appropriate trading sys
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Page 61 and 62: model species. However, high throug
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Page 65 and 66: 6 References ACRE (2007). Managing
Page 67 and 68: de Dorlodot S, Forster B, Pagès L,
Page 69 and 70: Hammer G, Cooper M, Tardieu F, Welc
Page 71 and 72: and quality. Australian Grapegrower
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Robinson RA & Sutherland WJ (2002).
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Vanderauwera S, De Block M, Van de
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7 Annexes 7.1 Project terms of refe
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Practical Action, UK. Professor Arp
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8 Glossary Abiotic stresses ACRE Ae
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Millenium Ecosystem Assessment Mole
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